Update README

README.md

@@ -108,7 +108,7 @@ Building Julia requires that the following software be installed:
 
 - **[GNU make]** — building dependencies.
 - **[gcc, g++][gcc]** — compiling and linking C, C++ (Need at least v4.6)
-- **[clang][clang]** — clang can be used instead of gcc (Need at least v3.1, Xcode 4.3.3 on OS X)
+- **[clang][clang]** — clang is the default compiler on OS X (Need at least v3.1, Xcode 4.3.3 on OS X)
 - **[gfortran][gcc]** — compiling and linking fortran libraries
 - **[git]** — contributions and version control.
 - **[perl]** — preprocessing of header files of libraries.
@@ -118,12 +118,12 @@ Building Julia requires that the following software be installed:
 
 Julia uses the following external libraries, which are automatically downloaded (or in a few cases, included in the Julia source repository) and then compiled from source the first time you run `make`:
 
-- **[LLVM]** — compiler infrastructure. Currently, julia requires LLVM 3.0.
+- **[LLVM]** — compiler infrastructure. Currently, julia requires LLVM 3.1.
 - **[FemtoLisp]** — packaged with julia source, and used to implement the compiler front-end.
 - **[readline]** — library allowing shell-like line editing in the terminal, with history and familiar key bindings.
 - **[fdlibm]** — a portable implementation of much of the system-dependent libm math library's functionality.
 - **[MT]** — a fast Mersenne Twister pseudorandom number generator library.
-- **[OpenBLAS]** — a fast, open, and maintained [basic linear algebra subprograms (BLAS)](https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprograms) library, based on [Kazushige Goto's](https://en.wikipedia.org/wiki/Kazushige_Goto) famous [GotoBLAS](https://www.tacc.utexas.edu/tacc-projects/gotoblas2/).
+- **[OpenBLAS]** — a fast, open, and maintained [basic linear algebra subprograms (BLAS)](https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprograms) library, based on [Kazushige Goto's](https://en.wikipedia.org/wiki/Kazushige_Goto) famous [GotoBLAS](https://www.tacc.utexas.edu/tacc-projects/gotoblas2/). The system provided BLAS and LAPACK are used on OS X.
 - **[LAPACK]** — a library of linear algebra routines for solving systems of simultaneous linear equations, least-squares solutions of linear systems of equations, eigenvalue problems, and singular value problems.
 - **[MKL]** (optional) – OpenBLAS & LAPACK may be replaced by Intel's MKL library.
 - **[AMOS]** — subroutines for computing Bessel and Airy functions.